Wide band side fed bifilar helix antenna caged in passive quadrifilar helix structure

In this paper a wideband side fed bifilar helix antenna enclosed in a cage of passive quadrifilar helix antenna (QHA) is presented. Simulation results show that the bandwidth of the side fed bifilar for VSWR ¿ 2 is increased from 1175-1240 MHz to that of 870-1535 MHz (greater than tenfold increase in bandwidth) by placing inside the passive QHA as compared to the side fed bifilar structure when simulated in isolation with predominantly omni-directional radiation pattern in the range of 500-1600 MHz. The measured results show that VSWR of the antenna is less than or equal to 2.4 from 281 MHz to greater than 2 GHz.